Semiconductor device having buried gate structure and method of fabricating the same

ABSTRACT

A semiconductor device includes a device isolation region defining an active region in a substrate, and gate structures buried in the active region of the substrate. At least one of the gate structures includes a gate trench, a gate insulating layer conformally formed on an inner wall of the gate trench, a gate barrier pattern conformally formed on the gate insulating layer disposed on a lower portion of the gate trench, a gate electrode pattern formed on the gate barrier pattern and filling the lower portion of the gate trench, an electrode protection layer conformally formed on the gate insulating layer disposed on an upper portion of the gate trench to be in contact with the gate barrier pattern and the gate electrode pattern, a buffer oxide layer conformally formed on the electrode protection layer, and a gate capping insulating layer formed on the buffer oxide layer to fill the upper portion of the gate trench.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority under 35 U.S.C. §119 to Korean PatentApplication No. 10-2014-0061198 flied on May 21, 2014, the disclosure ofwhich is incorporated by reference herein in its entirety.

TECHNICAL FIELD

Exemplary embodiments of the present inventive concept relate to asemiconductor device having a buried gate structure and a method offabricating the semiconductor device.

DISCUSSION OF RELATED ART

As a degree of integration of a semiconductor device graduallyincreases, a semiconductor device having a gate structure buried in asubstrate has been proposed. Existing gate electrode structures of aburied channel array transistor (BCAT) structure include a conductivegate electrode pattern and a gate barrier pattern, which are formed at alower portion of a gate trench, and a gate capping insulating layerformed at an upper portion of the gate trench. The gate cappinginsulating layer may be formed of a relatively hard insulating material,such as silicon nitride. Since a thermal expansion coefficient ofsilicon nitride may be significantly different from that of a siliconsubstrate, silicon nitride may cause a compressive stress to be appliedto the silicon substrate during subsequent thermal processes.

SUMMARY

Embodiments of the present inventive concept provide a semiconductordevice including a buried gate structure.

Exemplary embodiments of the present inventive concept provide asemiconductor device including a buried gate structure in which an upperend of a gate barrier pattern is recessed.

Exemplary embodiments of the present inventive concept provide asemiconductor device including a buried gate structure having a bufferoxide layer.

Exemplary embodiments of the present inventive concept provide asemiconductor device including a buried gate structure having a sourcearea and drain areas formed by a diffusion method.

Exemplary embodiments of the present inventive concept provide asemiconductor device including a buried gate structure capable ofreducing a compressive stress applied to an active region of asubstrate.

Exemplary embodiments of the present inventive concept provide a methodof fabricating a semiconductor device including a buried gate structure.

Exemplary embodiments of the present inventive concept provide a methodof fabricating a semiconductor device including a buried gate structurein which an upper end of a gate barrier pattern is recessed.

Exemplary embodiments of the present inventive concept provide a methodof fabricating a semiconductor device including a buried gate structurehaving a buffer oxide layer.

Exemplary embodiments of the present inventive concept provide a methodof fabricating a semiconductor device including a buried gate structurehaving a source area and drain areas formed by a diffusion method.

Exemplary embodiments of the present inventive concept provide a methodof fabricating a semiconductor device including a buried gate structurecapable of reducing a compressive stress applied to an active region ofa substrate.

In accordance with an aspect of the present inventive concept, asemiconductor device includes a device isolation region defining anactive region in a substrate, and gate structures buried in the activeregion of the substrate. At least one of the gate structures includes agate trench, a gate insulating layer conformally formed on an inner wallof the gate trench, a gate barrier pattern conformally formed on thegate insulating layer disposed on a lower portion of the gate trench, agate electrode pattern formed on the gate barrier pattern and fillingthe lower portion of the gate trench, an electrode protection layerconformally formed on the gate insulating layer disposed on an upperportion of the gate trench to be in contact with the gate barrierpattern and the gate electrode pattern, a buffer oxide layer conformallyformed on the electrode protection layer, and a gate capping insulatinglayer formed on the buffer oxide layer to fill the upper portion of thegate trench.

In accordance with an aspect of the present inventive concept, asemiconductor device includes gate structures buried in a substrate, abit-line contact plug formed on the substrate to be vertically alignedwith the substrate between the gate structures, a bit-line structureformed on the bit-line contact plug, and a spacer layer covering thebit-line structure.

In accordance with an aspect of the present inventive concept, asemiconductor device includes a device isolation region defining anactive region in a substrate, gate structures buried in the activeregion of the substrate, a bit-line contact plug formed on the substrateto be vertically aligned with the active region between the gatestructures, and a hit-line structure formed on the bit-line contact plug

Further details of exemplary embodiments are included in the detaileddescription and drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and other aspects of the present inventive concept will beapparent from the more particular description of embodiments of theinventive concept, as illustrated in the accompanying drawings in whichlike reference numerals may denote the same respective parts throughoutthe different views. The drawings are not necessarily to scale, emphasisinstead being placed upon illustrating the principles of the inventiveconcept. In the drawings:

FIGS. 1A and 1B are layouts schematically showing semiconductor devicesin accordance with embodiments of the inventive concept;

FIGS. 2A to 2F are vertical cross-sectional views taken along line I-I′of FIG. 1A or line II-II′ of FIG. 1B for describing semiconductordevices in accordance with various embodiments of the inventive concept;

FIGS. 3A to 8 are vertical cross-sectional views taken along line I-I′of FIG. 1A or line II-II′ of FIG. 1B for describing methods offabricating semiconductor devices in accordance with various embodimentsof the inventive concept;

FIG. 9 is a diagram conceptually showing a memory module including atleast one of the semiconductor devices in accordance with variousembodiments of the inventive concept;

FIG. 10 is a diagram conceptually showing a semiconductor module inaccordance with an embodiment of the inventive concept; and

FIGS. 11 and 12 are block diagrams conceptually showing electronicsystems in accordance with embodiments of the inventive concept.

DETAILED DESCRIPTION OF THE EMBODIMENTS

Various exemplary embodiments will now be described more fully withreference to the accompanying drawings in which some embodiments areshown. The inventive concept may, however, be embodied in differentforms and should not be construed as limited to the embodiments setforth herein. Rather, the exemplary embodiments are provided so thatthis disclosure is thorough and complete and fully conveys the inventiveconcept to those skilled in the art.

The terminology used herein to describe embodiments of the inventiveconcept is not intended to limit the scope of the inventive concept. Thearticles “a”, “an,” and “the” are singular in that they have a singlereferent; however, the use of the singular form in the present documentshould not preclude the presence of more than one referent. In otherwords, elements of the inventive concept referred to in the singularform may number one or more, unless the context clearly indicatesotherwise. It will be further understood that the terms “comprises,”“comprising,” “includes,” and/or “including,” when used herein, specifythe presence of stated features, integers, steps, operations, elements,and/or components, but do not preclude the presence or addition of oneor more other features, integers, steps, operations, elements,components, and/or groups thereof.

It will be understood that when an element or layer is referred to asbeing “on,” “connected to,” or “coupled to” another element or layer, itcan be directly on, connected to, or coupled to the other element orlayer or intervening elements or layers may be present. In the followingexplanation, the same reference numerals may denote the same componentsthroughout the specification and drawings.

Spatially relative terms, such as “beneath,” “below,” “lower,” “above,”“upper,” and the like may be used herein to describe the relationship ofone element or feature to another, as illustrated in the drawings. Itwill be understood that such descriptions are intended to encompassdifferent orientations in use or operation in addition to orientationsdepicted in the drawings. For example, if a device is turned over,elements described as “below” or “beneath” other elements or featureswould then be oriented “above” the other elements or features. Thus, theterm “below” is intended to mean both above and below, depending uponoverall device orientation.

Exemplary embodiments are described herein with reference tocross-sectional and/or planar illustrations that are schematicillustrations of idealized embodiments and intermediate structures. Inthe drawings, the sizes and relative sizes of layers and regions may beexaggerated for clarity. As such, variations from the shapes of theillustrations as a result, for example, of manufacturing techniquesand/or tolerances, are to be expected. Thus, embodiments should not beconstrued as limited to the particular shapes of regions illustratedherein but are to include deviations in shapes that result, for example,from manufacturing. For example, an implanted region illustrated as arectangle will, typically, have rounded or curved features and/or agradient of implant concentration at its edges rather than a binarychange from implanted to non-implanted region. Likewise, a buried regionformed by implantation may result in some implantation in the regionbetween the buried region and the surface through which the implantationtakes place. Thus, the regions illustrated in the figures are schematicin nature and their shapes are not intended to illustrate the actualshape of a region of a device and are not intended to limit the scope ofthe present inventive concept.

Like numerals may refer to like elements throughout the specificationand drawings. Accordingly, the same numerals and similar numerals can bedescribed with reference to other drawings, even if not specificallydescribed in a corresponding drawing. Further, when a numeral is notmarked in a drawing, the numeral can be described with reference toother drawings.

FIGS. 1A and 1B are layouts schematically showing semiconductor devicesin accordance with embodiments of the inventive concept.

Referring to FIGS. 1A and 1B, semiconductor devices 100 may includebit-lines 50L, extending in an X-direction, gate lines 20L extending ina Y-direction perpendicular to the X-direction, and bar-shaped activeregions 11 extending in a Z-direction diagonal to the X-direction andthe Y-direction. The semiconductor devices 100 may include bit-linecontact plugs 40 overlapping center areas of the active regions 11intersecting the bit-lines 501, and capacitor contact plugs 60overlapping both ends of the active regions 11.

The active regions 11 may be arranged to be staggered from each other inthe Y-direction as shown in FIG. 1A, or arranged in parallel as shown inFIG. 1B.

Referring further to FIG. 1B, device isolation lines 12L, extending inthe Y-direction to be parallel to the gate lines 20L, may be furtherdisposed between the active regions 11.

FIGS. 2A to 2F are vertical cross-sectional views taken along line I-Fof FIG. 1A or line II-II′ of FIG. 1B for describing semiconductordevices 100A to 100F in accordance with embodiments of the inventiveconcept.

Referring to FIG. 2A, a semiconductor device 100A may include deviceisolation regions 12 formed in a substrate 10, gate structures 20, abit-line structure 50, and capacitor structures 80. The semiconductordevice 100A may include a hit-line contact plug 40 formed between thesubstrate 10 and the bit-line structure 50. The semiconductor device100A may include capacitor contact plugs 60 formed between the substrate10 and the capacitor structures 80. The semiconductor device 100A mayinclude a lower interlayer insulating layer 32, a hole mask layer 33, aspacer layer 34, an upper interlayer insulating layer 35, an etch stoplayer 36, and a capacitor capping insulating layer 38. The semiconductordevice 100A may include a trench mask layer 31.

The device isolation regions 12 may include device isolation trenches 12a formed in the substrate 10, and a device isolation insulating material12 b filling the device isolation trenches 12 a. The device isolationinsulating material 12 b may include silicon oxide. The device isolationregions 12 may define an active region 11. The active region 11 mayinclude a source area us between the gate structures 20, and drain areas11 d between the gate structures 20 and the device isolation regions 12.The source area. 1 is and the drain areas 11 d may include N-typeimpurities, such as phosphorus (P) and/or arsenic (As), respectively.

The gate structure 20 may include a gate insulating layer 22, a gatebarrier pattern 23, a gate electrode pattern 24, an electrode protectionlayer 25, a buffer oxide layer 26, and a gate capping insulating layer27 which are formed in a gate trench 21. The gate structures 20 may beburied in the active region 11 of the substrate 10.

The gate trench 21 may be formed from a surface of the substrate 10toward the inside of the substrate 10.

The gate insulating layer 22 may be conformally formed on an entireinner wall of the gate trench 21. The gate insulating layer 22 mayinclude, for example, silicon oxide, silicon nitride, siliconoxynitride, or a metal oxide. The metal oxide may include, for example,hafnium oxide, aluminum oxide, or titanium oxide.

The gate barrier pattern 23 may be conformally formed on the gateinsulating layer 22. The gate barrier pattern 23 may be formed only on alower portion of the gate trench 21. The gate barrier pattern 23 mayinclude a barrier metal compound, such as, for example, titanium nitride(TiN) or tantalum nitride (TaN).

The gate electrode pattern 24 may be formed on the gate barrier pattern23 to partially fill the gate trench 21. For example, the gate electrodepattern 24 may fill the lower portion of the gate trench 21. The gateelectrode pattern 24 may include a metal, such as tungsten or copper.

An upper end of the gate barrier pattern 23 may be recessed to be lowerthan an upper end of the gate electrode pattern 24. When the upper endof the gate barrier pattern 23 is recessed, a distance between the gateelectrode pattern 24 and the source area 11 s and a distance between thegate electrode pattern 24 and the drain areas 11 d may increase.Accordingly, a gate induced drain leakage (GIDL) current generated byturn-on of the gate structure 20 may decrease.

The electrode protection layer 25 may be conformally formed on the gateinsulating layer 22 disposed on an upper portion of the gate trench 21.The electrode protection layer 25 may be formed on the upper end of therecessed gate barrier pattern 23. For example, a portion of theelectrode protection layer 25 may be interposed between the gateelectrode pattern 24 and the gate insulating layer 22. The electrodeprotection layer 25 may include silicon nitride. When the electrodeprotection layer 25 is interposed between the gate electrode pattern 24and the buffer oxide layer 26, diffusion of oxygen atoms or oxygen ionsfrom the buffer oxide layer 26 to the gate electrode pattern 24 may bereduced or prevented.

The buffer oxide layer 26 may be conformally formed on the electrodeprotection layer 25. The buffer oxide layer 26 may include siliconoxide. For example, the buffer oxide layer 26 may include a dopedsilicon oxide such as phosphorous silicate glass (PSG), or dopants suchas, for example, phosphorous (P). The buffer oxide layer 26 may be asource for ion implantation. In an exemplary embodiment, the dopantsincluded in the buffer oxide layer 26 may diffuse into the active region11 during a manufacturing process and form the source area 11 s and thedrain areas 11 d. Accordingly, when an ion-implantation process in whichions are physically implanted is excluded, physical damage to a surfaceof the active region 11 may be reduced or prevented, and a dopingprofile gradually changing according to a distance may be obtained.

The gate capping insulating layer 27 may be formed on the buffer oxidelayer 26 to fill the gate trench 21. The gate capping insulating layer27 may include silicon nitride.

The gate capping insulating layer 27 may apply a compressive stress tothe active region 11 of the substrate 10. The buffer oxide layer 26 mayreduce the compressive stress. Accordingly, reduction of N-type carriermobility in the active region 11 due to the compressive stress may bemitigated.

When the buffer oxide layer 26 is softer and more flexible than the gatecapping insulating layer 27, negative phenomena occurring due to adifference in thermal expansion coefficients between the substrate 10and the gate capping insulating layer 27 may be reduced or prevented.

The bit-line contact plug 40 may be formed on the source area 11 s ofthe active region 11 of the substrate 10. A bottom surface of thebit-line contact plug 40 may be located inside the substrate 10. Forexample, the bottom surface of the bit-line contact plug 40 may protrudedownward to be lower than an upper surface of the substrate 10. Outersides of the bottom surface of the bit-line contact plug 40 may be incontact with the gate structures 20. For example, a side of the bottomsurface the bit-line contact plug 40 and/or a lower portion of a sidesurface of the bit-line contact plug 40 may be in contact with the gateinsulating layer 22, electrode protection layer 25, buffer oxide layer26, and gate capping insulating layer 27 of the gate structures 20. Inother words, an upper surface of the source area 11 s of the activeregion 11 in the substrate 10 may be recessed so that the bottom surfaceof the bit-line contact plug 40 is located inside the substrate 10. Inan embodiment, upper surfaces of the gate insulating layer 22, theelectrode protection layer 25, the buffer oxide layer 26, and the gatecapping insulating layer 27 of the gate structures 20 may be partlyrecessed and slanted. For example, portions of the gate structures 20,which are exposed without being vertically aligned or overlapped withthe bit-line structure 50, may be slanted forward. A side of an uppersurface of the bit-line contact plug 40 may be recessed and slanted.When outer portions of the upper surface of the bit-line contact plug 40are recessed, a short between the bit-line contact plug 40 and otherconductive components may be reduced or prevented. A horizontal width ofthe bit-line contact plug 40 may be greater than a distance between thegate structures 20, that is, a horizontal width of the source area 11 s.The bit-line contact plug 40 may electrically connect the source area 11s of the active region 11 in the substrate 10 to the bit-line structure50.

A protection insulating layer 45 may be formed on the slanted surfacesof the bit-line contact plug 40. The protection insulating layer 45 mayinclude silicon oxide, for example, a native oxide. The protectioninsulating layer 45 may reduce or prevent an electrical short betweenthe bit-line contact plug 40 and the other conductive components, andprotect the bit-line contact plug 40 from being damaged physically andchemically during a manufacturing process.

The trench mask layer 31 may be formed on the substrate 10 and/or thedevice isolation regions 12 to surround the side surfaces of thebit-line contact plug 40 and the capacitor contact plugs 60. Uppersurfaces of the gate structures 20 and an upper surface of the trenchmask layer 31 may be coplanar. The trench mask layer 31 may includesilicon oxide or silicon nitride.

The lower interlayer insulating layer 32 may be formed on the trenchmask layer 31 to surround the side surfaces of the bit-line contact plug40 and the capacitor contact plugs 60. The lower interlayer insulatinglayer 32 may include silicon oxide or silicon nitride. For example, whenthe trench mask layer 31 and the lower interlayer insulating layer 32are formed of the same material, a boundary between the trench masklayer 31 and the lower interlayer insulating layer 32 may disappear.

The bit-line structure 50 may include a bit-line barrier pattern 53, abit-line electrode pattern 54, and a bit-line capping pattern 55. Thebit-line barrier pattern 53 may be in contact with and electricallyconnected to the bit-line contact plug 40. The bit-line barrier pattern53 may include a metal or a metal compound, such as titanium (Ti),titanium nitride (TN), titanium silicide (TiSi), tantalum (Ta), tantalumnitride (TaN), tantalum silicide (TaSi), nickel silicide (NiSi), cobaltsilicide (CoSi), tungsten nitride (WN), or tungsten silicide (WSi). Thebit-line electrode pattern 54 may include a metal, such as tungsten orcopper. The bit-line capping pattern 55 may include silicon nitride.Sidewalls of the bit-line barrier pattern 53, the bit-line electrodepattern 54, and the bit-line capping pattern 55 may be verticallyaligned.

The spacer layer 34 may surround the bit-line structure 50. For example,the spacer layer 34 may be conformally formed on top and side surfacesof the bit-line structure 50. The spacer layer 34 may cover the slantlyrecessed surfaces of the bit-line contact plug 40. The spacer layer 34may horizontally extend onto the lower interlayer insulating layer 32.The spacer layer 34 may include silicon nitride.

The upper interlayer insulating layer 35 may surround side surfaces ofthe spacer layer 34. An upper surface of the spacer layer 34 and anupper surface of the upper interlayer insulating layer 35 may becoplanar.

The capacitor contact plugs 60 may be aligned to vertically pass throughthe upper interlayer insulating layer 35, the spacer layer 34, the lowerinterlayer insulating layer 32, and the trench mask layer 31 to berespectively connected to the drain areas 11 d of the active region 11in the substrate 10. Bottom surfaces of the capacitor contact plugs 60may be located inside the substrate 10. Outer sides of the bottomsurfaces of the capacitor contact plugs 60 may be in contact with thegate structures 20 and the device isolation regions 12. For example, thecapacitor contact plugs 60 may be in contact with the gate insulatinglayer 22, the electrode protection layer 25, the buffer oxide layer 26,and the gate capping insulating layer 27 of the gate structures 20, inother words, upper surfaces of the drain areas 11 d of the active region11 in the substrate 10 may be recessed so that the bottom surfaces ofthe capacitor contact plugs 60 are located inside the substrate 10. Inaddition, upper surfaces of the gate insulating layer 22, the electrodeprotection layer 25, the buffer oxide layer 26, and the gate cappinginsulating layer 27 of the gate structures 20 may be partly recessed.Horizontal widths of the capacitor contact plugs 60 may be greater thana distance between the gate structures 20 and the device isolationregions 12, that is, horizontal widths of the drain areas 11 d. Thecapacitor contact plugs 60 may electrically connect the drain areas 11 dof the active region 11 in the substrate 10 to the capacitor structures80, respectively. The upper surfaces of the spacer layer 34 and theupper interlayer insulating layer 35, and/or an upper surface of thecapacitor contact plug 60 may be coplanar.

The etch stop layer 36 may be formed on the bit-line structure 50 andthe upper interlayer insulating layer 35. The etch stop layer 36 may beformed on an upper portion of the bit-line structure 50, for example, onthe bit-line capping pattern 55 or the spacer layer 34. The etch stoplayer 36 may include, for example, silicon nitride.

Each of the capacitor structures 80 may include a capacitor lowerelectrode 81, a capacitor dielectric layer 83, and a capacitor upperelectrode 85. The capacitor lower electrodes 81 may be electricallyconnected to and vertically aligned with the capacitor contact plugs 60,respectively. The capacitor lower electrode 81 may vertically passthrough the etch stop layer 36. The capacitor lower electrode 81 mayinclude a conductive material, such as a doped polysilicon, a metal, ora metal compound. The capacitor dielectric layer 83 may conformallycover a surface of the capacitor lower electrode 81. For example, thecapacitor dielectric layer 83 may be formed on top and side surfaces ofthe capacitor lower electrode 81. The capacitor dielectric layer 83 mayextend onto the etch stop layer 36. In other words, the capacitordielectric layer 83 may be conformally formed on a surface of the etchstop layer 36. The capacitor dielectric layer 83 may include one of ametal oxide, such as hafnium oxide, aluminum oxide, titanium oxide,tantalum oxide, ruthenium oxide, and lanthanum oxide, silicon oxide, orsilicon nitride. The capacitor upper electrode 85 may be conformallyformed on the capacitor dielectric layer 83. The capacitor upperelectrode 85 may include a metal or a metal compound.

The capacitor capping insulating layer 38 may fill a gap between thecapacitor structures 80 and cover the capacitor structures 80. Thecapacitor capping insulating layer 38 may include silicon oxide.

As described above, when the upper end of the gate barrier pattern 23 isrecessed to be lower than the upper end of the gate electrode pattern24, the distance between the gate electrode pattern 24 and the sourcearea 11 s and the distance between the gate electrode pattern 24 and thedrain areas 11 d may increase. Accordingly, a GIDL current generated byturn-on of the gate structure 20 may decrease.

When the electrode protection layer 25 is interposed between the gateelectrode pattern 24 and the buffer oxide layer 26, diffusion of oxygenatoms or oxygen ions from the buffer oxide layer 26 to the gateelectrode pattern 24 to oxidize the gate electrode pattern 24 may bereduced or prevented.

When the buffer oxide layer 26 includes N-type dopants such asphosphorus (P), the source area 11 s and the drain areas 11 d may beformed using a diffusion process. When the buffer oxide layer 26 issofter and more flexible than the electrode protection layer 25 and thegate capping insulating layer 27, a compressive stress applied to theactive region 11 from the gate capping insulating layer 27 may bereduced, and reduction of the N-type carrier mobility in the activeregion 11 may be reduced or prevented.

Referring to FIG. 2B, a semiconductor device 100B in accordance with anembodiment of the inventive concept may include device isolation regions12 formed in a substrate 10, gate structures 20, a bit-line structure50, and capacitor structures 80. The semiconductor device 100B mayinclude a bit-line contact plug 40 formed between the substrate 10 andthe bit-line structure 50. The semiconductor device 100B may includecapacitor contact plugs 60 between the substrate 10 and the capacitorstructures 80. The semiconductor device 100B may include a lowerinterlayer insulating layer 32, a hole mask layer 33, a spacer layer 34,an upper interlayer insulating layer 35, an etch stop layer 36, and acapacitor capping insulating layer 38. The lower interlayer insulatinglayer 32 may be formed, for example, directly on the substrate 10 and/orthe device isolation regions 12. Components which are not describedherein may be understood with reference to FIG. 2A.

Referring to FIG. 2C, a semiconductor device 1000 in accordance with anembodiment of the inventive concept may include device isolation regions12 formed in a substrate 10, gate structures 20, a bit-line structure50, and capacitor structures 80. The semiconductor device 100C mayinclude a bit-line contact plug 40 formed between the substrate 10 andthe bit-line structure 50. The semiconductor device 1000 may includecapacitor contact plugs 60 formed between the substrate 10 and thecapacitor structures 80. The semiconductor device 100C may include alower interlayer insulating layer 32, a hole mask layer 33, a spacerlayer 34, an upper interlayer insulating layer 35, an etch stop layer36, and a capacitor capping insulating layer 38. The semiconductordevice 1000 may include a trench mask layer 31.

The gate structures 20 may include a gate insulating layer 22, a gatebarrier pattern 23, a gate electrode pattern 24, a buffer oxide layer26, and a gate capping insulating layer 27 which are formed in a gatetrench 21. The buffer oxide layer 26 may be directly and conformallyformed on the gate insulating layer 22.

An upper end of the gate barrier pattern 23 may be recessed to be lowerthan an upper end of the gate electrode pattern 24. The buffer oxidelayer 26 may be formed on the upper end of the recessed gate barrierpattern 23. For example, a portion of the buffer oxide layer 26 may beinterposed between the gate electrode pattern 24 and the gate insulatinglayer 22. The buffer oxide layer 26 may contact the gate barrier pattern23 and the gate electrode pattern 24. When the gate electrode pattern 24includes an oxidation resistant metal, the electrode protection layer 25shown in FIGS. 2A and 2B may be omitted.

Referring to FIG. 2D, a semiconductor device 100D in accordance with anembodiment of the inventive concept may include device isolation regions12 formed in a substrate 10, gate structures 20, a bit-line structure50, and capacitor structures 80. The semiconductor device 100D mayinclude a bit-line contact plug 40 formed between the substrate 10 andthe bit-line structure 50. The semiconductor device 100D may includecapacitor contact plugs 60 formed between the substrate 10 and thecapacitor structures 80. The semiconductor device 100D may include alower interlayer insulating layer 32, a hole mask layer 33, a spacerlayer 34, an upper interlayer insulating layer 35, an etch stop layer36, and a capacitor capping insulating layer 38.

The gate structures 20 may include a gate insulating layer 22, a gatebarrier pattern 23, a gate electrode pattern 24, a buffer oxide layer26, and a gate capping insulating layer 27 which are formed in a gatetrench 21. The buffer oxide layer 26 may be directly and conformallyformed on the gate insulating layer 22. The buffer oxide layer 26 maycontact the gate barrier pattern 23 and the gate electrode pattern 24.When the gate electrode pattern 24 includes an oxidation resistantmetal, the electrode protection layer 25 shown in FIGS. 2A and 2B may beomitted.

The lower interlayer insulating layer 32 may be formed, for example,directly on the substrate 10 and/or the device isolation regions 12.

Referring to FIG. 2E, a semiconductor device 100E in accordance with anembodiment of the inventive concept may include device isolation regions12 formed in a substrate 10, gate structures 20, a bit-line structure50, and capacitor structures 80. The semiconductor device 100E mayinclude a bit-line contact plug 40 formed between the substrate 10 andthe bit-line structure 50. The semiconductor device 100E may includecapacitor contact plugs 60 formed between the substrate 10 and thecapacitor structures 80. The semiconductor device 100E may include alower interlayer insulating layer 32, a hole mask layer 33, a spacerlayer 34, an upper interlayer insulating layer 35, an etch stop layer36, and a capacitor capping insulating layer 38. The semiconductordevice 100E may include a trench mask layer 31.

The gate structures 20 may include a gate insulating layer 22, a gatebarrier pattern 23, a gate electrode pattern 24, an electrode protectionlayer 25, a buffer oxide layer 26, and a gate capping insulating layer27 which are formed in a gate trench 21. An upper end of the gatebarrier pattern 23 may be recessed to be lower than an upper end of thegate electrode pattern 24.

The electrode protection layer 25 may be interposed between the gateelectrode pattern 24 and the buffer oxide layer 26. The electrodeprotection layer 25 may have a substantially planar surface. Theelectrode protection layer 25 may cover an upper surface of the gateelectrode pattern 24, and may be disposed on the recessed gate barrierpattern 23 interposed between the gate insulating layer 22 and the gateelectrode pattern 24. For example, the electrode protection layer 25need not be substantially formed on the gate insulating layer 22disposed on sidewalls of the gate trench 21.

The buffer oxide layer 26 may be directly and conformally formed on thegate insulating layer 22 disposed on the sidewalls of the gate trench21. The buffer oxide layer 26 need not be in contact with the gatebarrier pattern 23 and the gate electrode pattern 24.

The gate capping insulating layer 27 may be in contact with the gateinsulating layer 22 at an upper portion of the gate trench 21.

Referring to FIG. 2F, a semiconductor device 100F in accordance with anembodiment of the inventive concept may include device isolation regions12 formed in a substrate 10, gate structures 20, a bit-line structure50, and capacitor structures 80. The semiconductor device 100E mayinclude a bit-line contact plug 40 formed between the substrate 10 andthe bit-line structure 50. The semiconductor device 100F may includecapacitor contact plugs 60 formed between the substrate 10 and thecapacitor structures 80. The semiconductor device 100F may include alower interlayer insulating layer 32, a hole mask layer 33, a spacerlayer 34, an upper interlayer insulating layer 35, an etch stop layer36, and a capacitor capping insulating layer 38.

The gate structures 20 may include a gate insulating layer 22, a gatebarrier pattern 23, a gate electrode pattern 24, a buffer oxide layer26, and a gate capping insulating layer 27 which are formed in a gatetrench 21.

An upper end of the gate barrier pattern 23 may be recessed to be lowerthan an upper end of the gate electrode pattern 24.

The electrode protection layer 25 may be interposed between the gateelectrode pattern 24 and the buffer oxide layer 26. The electrodeprotection layer 25 may have a substantially planar surface. Theelectrode protection layer 25 may cover an upper surface of the gateelectrode pattern 24, and may be disposed on the recessed gate barrierpattern 23 interposed between the gate insulating layer 22 and the gateelectrode pattern 24. For example, the electrode protection layer 25need not be substantially formed on the gate insulating layer 22disposed on sidewalls of the gate trench 21.

In an embodiment, the buffer oxide layer 26 may be directly andconformally formed on the gate insulating layer 22 disposed on thesidewalls of the gate trench 21. The buffer oxide layer 26 need not bein contact with the gate barrier pattern 23 and the gate electrodepattern 24 according to an embodiment.

The gate capping insulating layer 27 may be in contact with the gateinsulating layer 22 at an upper portion of the gate trench 21.

The lower interlayer insulating layer 32 may be directly formed on thesubstrate 10 and/or the device isolation regions 12.

In the semiconductor devices 100E and 100F described in FIGS. 2E and 2F,an area in which the electrode protection layer 25 is in contact withthe sidewalls of the gate trench 21 is minimized, and a compressivestress applied to the source area 11 s and drain areas 11 d of theactive region 11 by the electrode protection layer 25 may be minimized.

FIGS. 3A to 3O are vertical cross-sectional views taken along line I-I′of FIG. 1A or line II-II′ of FIG. 1B for describing a method offabricating a semiconductor device in accordance with an embodiment ofthe inventive concept.

Referring to FIG. 3A, a method of fabricating a semiconductor device100A in accordance with an embodiment of the inventive concept mayinclude forming device isolation regions 12 defining an active region 11in a substrate 10 by performing a shallow trench isolation (STI)process, for example. The STI process may include forming a deviceisolation trench 12 a in the substrate 10 and filling the deviceisolation trench 12 a with a device isolation insulating material 12 bsuch as silicon oxide.

Referring to FIG. 3B, the method may include forming a trench mask layer31 on the substrate 10, and forming gate trenches 21 in the substrate 10by performing an etching process using the trench mask layer 31 as anetch mask. The trench mask layer 31 may include a relatively densesilicon oxide, such as silicon oxide formed in a high density plasma(HDP) process.

Referring to FIG. 3C, the method may include conformally forming a gateinsulating layer 22 on inner walls of the gate trenches 21 and a surfaceof the trench mask layer 31. The gate insulating layer 22 may includesilicon oxide or a metal oxide. The metal oxide may include hafniumoxide, aluminum oxide, or titanium oxide. The gate insulating layer 22may be formed using, for example, an atomic layered deposition (ALD)process and/or a thermal oxidation process. When the gate insulatinglayer 22 is formed using a thermal oxidation process, the gateinsulating layer 22 need not be formed on a surface of the trench masklayer 31.

Referring to FIG. 3D, the method may include conformally forming a gatebarrier layer 23 a on the gate insulating layer 22 and forming a gateelectrode layer 24 a filling the gate trench 21 on the gate barrierlayer 23 a. The gate barrier layer 23 a may be formed by performing anALD process. The gate electrode layer 24 a may be formed by performingan ALD or chemical vapor deposition (CVD) process. The gate barrierlayer 23 a may include a barrier metal compound, such as titaniumnitride TN or tantalum nitride TaN. The gate electrode layer 24 a mayinclude a metal such as tungsten or copper.

Referring to FIG. 3E, the method may include forming a gate electrodepattern 24 and a gate barrier pattern 23 by partially removing upperportions of the gate barrier layer 23 a and the gate electrode layer 24a in the gate trench 21 by performing an etch back process. An uppersurface of the gate electrode pattern 24 may be located at a higherlevel than an upper end of the gate barrier pattern 23. In other words,the upper end of the gate barrier pattern 23 may be recessed to be lowerthan the upper surface of the gate electrode pattern 24. Accordingly, agap g may be formed between the gate insulating layer 22 and the gateelectrode pattern 24.

The etch back process may include a wet etching process. The wet etchingprocess may be executed one or two times using an etching solutionincluding a first etchant by which the gate electrode layer 24 a ismainly removed and a second etchant by which the gate barrier layer 23 ais mainly etched. For example, the wet etching process may includeperforming a first etching process using an etching solution includingthe first etchant, and subsequently performing a second etching processusing an etching solution including the second etchant. The firstetchant may include water, hydrogen peroxide (H₂O₂), and/or ammonium(NH₄). The second etchant may include water and sulfuric acid (H₂SO₄).The second etchant may include H₂O₂ and/or NH₄.

Referring to FIG. 3F, the method may include forming an electrodeprotection layer 25 on the gate insulating layer 22 and the gateelectrode pattern 24 in the gate trench 21, forming a buffer oxide layer26 on the electrode protection layer 25, and forming a gate cappinginsulating layer 27 on the buffer oxide layer 26.

The electrode protection layer 25 may fill the gap g. The electrodeprotection layer 25 may also be formed on the trench mask layer 31. Theelectrode protection layer 25 may be conformally formed using an ALDprocess. The electrode protection layer 25 may include silicon nitride.

The buffer oxide layer 26 may be conformally formed using an ALDprocess. The buffer oxide layer 26 may include a dopant. The dopant maysufficiently include N-type impurities, such as phosphorus (P) orarsenic (As), for example, phosphosilicate glass (PSG) and an N-dopedoxide. For example, the buffer oxide layer 26 may include phosphorus (P)up to about 20% of a total weight or a volume thereof. The buffer oxidelayer 26 need not substantially include P-type impurities such as boron(B).

The gate capping insulating layer 27 may fully fill the gate trench 21.The gate capping insulating layer 27 may include silicon nitride.

In an embodiment, the method may include forming a source area 11 s anddrain areas 11 d by performing a thermal annealing process. The sourcearea 11 s and the drain areas 11 d may be formed in such a manner thatthe dopant in the buffer oxide layer 26 is diffused into the substrate10. The source area 11 is and the drain areas 11 d formed by thediffusion process may have a gradient dopant concentration according toa distance (from a surface of the substrate 10), and may thereby havestable electrical properties. When an ion-implantation process by whichthe active region 11 is physically damaged is not performed, the sourcearea 11 s and the drain areas 11 d may retain their physical andelectrical properties.

When the gate capping insulating layer 27 and/or the electrodeprotection layer 25 include(s) silicon nitride, the gate cappinginsulating layer 27 may apply a compressive stress to the substrate 10.When the buffer oxide layer 26 is more flexible than the gate cappinginsulating layer 27 and the electrode protection layer 25, thecompressive stress may be mitigated. When the compressive stress isapplied to the substrate 10, electron mobility in the substrate 10 maybe lowered. When the buffer oxide layer 26 reduces the compressivestress, reduction of the electron mobility may be mitigated.

Referring to FIG. 3G, the method may include removing the gate cappinginsulating layer 27, the buffer oxide layer 26, and the electrodeprotection layer 25 which are disposed on the trench mask layer 31 byperforming a planarization process, and forming a gate structure 20including the gate insulating layer 22, the gate barrier pattern 23, thegate electrode pattern 24, the electrode protection layer 25, the bufferoxide layer 26, and the gate capping insulating layer 27 which areformed in the gate trench 21. The planarization process may include achemical mechanical polishing (CMP) process. An upper surface of thetrench mask layer 31 may be exposed.

Referring to FIG. 3H, the method may include forming a lower interlayerinsulating layer 32 and a hole mask layer 33 on the gate structure 20and the trench mask layer 31. The lower interlayer insulating layer 32may include silicon oxide. The hole mask layer 33 may include siliconnitride. The hole mask layer 33 may include a hole h vertically alignedwith the source area 11 s of the active region 11 disposed between thegate structures 20.

Referring to FIG. 3I, the method may include forming a bit-line contacthole 40 h vertically aligned with the hole h and exposing the sourcearea us of the active region 11 in the substrate 10 by performing anetching process using the hole mask layer 33 as an etch mask. A bottomsurface of the bit-line contact hole 40 h may be recessed to be lowerthan a surface of the substrate 10. The hole mask layer 33 may becomethinner. During the etching process, the gate capping insulating layer27, the buffer oxide layer 26, and the electrode protection layer 25 mayprotect the gate electrode pattern 24 from an etchant.

Referring to FIG. 3J, the method may include forming a bit-line contactplug 40 in the bit-line contact hole 40 h. The bit-line contact plug 40may be formed by performing an epitaxial growth process or a depositionprocess and further performing an etch back process. During the etchback process, the bit-line contact plug 40 may become shallower. Thebit-line contact plug 40 may include a doped polysilicon, a metal, or ametal silicide. When the bit-line contact plug 40 includes a metalsilicide, the bit-line contact plug 40 may be formed by a polysiliconforming process, a metal layer forming process, and a silicidationprocess.

Referring to FIG. 3k , the method may include forming a bit-line barrierlayer 53 a, a bit-line electrode layer 54 a, and a bit-line cappinglayer 55 a by performing a deposition process on the bit-line contactplug 40. The bit-line barrier layer 53 a may include a metal or a metalcompound, such as titanium (Ti), titanium nitride (TiN), titaniumsilicide (TiSi), tantalum (Ta), tantalum nitride (TaN), tantalumsilicide (TaSi), nickel silicide (NiSi), cobalt silicide (CoSi),tungsten nitride (WN), or tungsten silicide (WSi). The bit-lineelectrode layer 54 a may include a metal, such as tungsten or copper.The bit-line capping layer 55 a may include silicon nitride.

Referring to FIG. 3L, the method may include forming a bit-linestructure 50 including a bit-line barrier pattern 53, a bit-lineelectrode pattern 54, and a bit-line capping pattern 55 by etching thebit-line capping layer 55 a, the bit-line electrode layer 54 a, and thebit-line barrier layer 53 a. The bit-line contact plug 40 adjacent tobit-line structure 50 may have a slantly recessed dent.

Referring to FIG. 3M, the method may include forming a protectioninsulating layer 45 on a slanted surface of the exposed bit-line contactplug 40, and forming a spacer layer 34 surrounding the bit-linestructure 50. The protection insulating layer 45 may include siliconoxide. For example, the protection insulating layer 45 may include anative oxide. The spacer layer 34 may include silicon nitride formed byperforming an ALD process or a CVD process. The spacer layer 34 may fillthe dent d on the slantly recessed surface of the bit-line contact plug40.

Referring to FIG. 3N, the method may include forming an upper interlayerinsulating layer 35 on the spacer layer 34, forming capacitor contactholes 60 h by etching the upper interlayer insulating layer 35, thespacer layer 34, the lower interlayer insulating layer 32, and thetrench mask layer 31, and forming capacitor contact plugs 60 filling thecapacitor contact holes 60 h.

The upper interlayer insulating layer 35 may include silicon oxideformed by a deposition process. Before the capacitor contact holes 60 hare formed, a CMP process for planarizing the upper interlayerinsulating layer 35 may be performed.

The capacitor contact holes 60 h may be vertically aligned with thedrain areas 11 d, respectively. Bottom surfaces of the capacitor contactholes 60 h may be recessed to be lower than the surface of the substrate10. While the etching process is performed, the gate capping insulatinglayer 27, the buffer oxide layer 26, and the electrode protection layer25 may protect the gate electrode pattern 24 from being damaged by anetchant.

The method may include performing a planarization process such as a CMPprocess in order for upper surfaces of the capacitor contact plugs 60 tobe coplanar with an upper surface of the spacer layer 34 or bit-linecapping pattern 55. The capacitor contact plugs 60 may include one of adoped polysilicon, a metal, a metal silicide, and a metal compound.

Referring to FIG. 3O, the method may include forming an etch stop layer36 on the capacitor contact plugs 60 and the spacer layer 34 or thebit-line capping pattern 55, forming a molding oxide layer 37 on theetch stop layer 36, and forming capacitor electrode holes 81 hvertically passing through the molding oxide layer 37 and the etch stoplayer 36 to expose the upper surface of the capacitor contact plugs 60.

The etch stop layer 36 may include silicon nitride formed by adeposition process. The molding oxide layer 37 may include siliconoxide.

Referring to FIG. 3P, the method may include forming capacitor lowerelectrodes 81 filling the capacitor electrode holes 81 h, and removingthe molding oxide layer 37. The capacitor lower electrodes 81 mayinclude one of a doped polysilicon, a metal, and a metal silicide whichare formed by an ALD process or a CVD process.

Referring to FIG. 3Q, the method may include forming a capacitorstructure 80 by conformally forming a capacitor dielectric layer 83 onsurfaces of the capacitor lower electrodes 81 and conformally forming acapacitor upper electrode 85 on the capacitor dielectric layer 83. Thecapacitor dielectric layer 83 may include a metal oxide, such as hafniumoxide, aluminum oxide, titanium oxide, tantalum oxide, ruthenium oxide,or lanthanum oxide, silicon oxide, or silicon nitride which are formedby an ALD process. The capacitor upper electrode 85 may include a metalor a metal compound formed by an ALD process.

Referring to FIG. 2A, the method may include forming a capacitor cappinginsulating layer 38 filling a gap between the capacitor structures 80and covering the capacitor structures 80 on the capacitor upperelectrode 85. The capacitor capping insulating layer 38 may includesilicon oxide formed by, for example, a CVD process.

FIGS. 4A to 4D are vertical cross-sectional views taken along line I-I′of FIG. 1A or liras II-II′ of FIG. 1B for describing a method offabricating a semiconductor device in accordance with an embodiment ofthe inventive concept.

Referring to FIG. 4A, a method of fabricating a semiconductor device100B in accordance with an embodiment of the inventive concept mayinclude, by performing the processes described with reference to FIGS.3A to 3G, forming device isolation regions 12 defining an active region11 in a substrate 10, forming a trench mask layer 31 on the substrate10, forming gate trenches 21 in the substrate 10 by performing anetching process using the trench mask layer 31 as an etch mask,conformally forming a gate insulating layer 22 on inner walls of thegate trenches 21 and a surface of the trench mask layer 31, conformallyforming a gate harrier layer 23 a on the gate insulating layer 22,forming a gate electrode layer 24 a filling the gate trench 21 on thegate barrier layer 23 a, forming a gate electrode pattern 24 and a gatebarrier pattern 23 by partially removing upper portions of the gatebarrier layer 23 a and the gate electrode layer 24 a in the gate trench21 by performing an etchback process, forming an electrode protectionlayer 25 on the gate insulating layer 22 and the gate electrode pattern24 in the gate trench 21, forming a buffer oxide layer 26 on theelectrode protection layer 25, forming a gate capping insulating layer27 filling the gate trench 21 on the buffer oxide layer 26, forming asource area 11 s and drain areas 11 d, and forming a gate structure 20including the gate insulating layer 22, the gate barrier pattern 23, thegate electrode pattern 24, the electrode protection layer 25, the bufferoxide layer 26, and the gate capping insulating layer 27 in the gatetrench 21 by removing the gate capping insulating layer 27, the bufferoxide layer 26, the electrode protection layer 25, and the trench masklayer 31 which are disposed on the substrate 10 by performing aplanarization process. The surface of the substrate 10 may be exposed.For example, the trench mask layer 31 may be fully removed.

Referring to FIG. 4B, the method may include forming a lower interlayerinsulating layer 32 and a hole mask layer 33 on the gate structure 20and the exposed surface of the substrate 10, by performing the processesdescribed with reference to FIG. 3H.

Referring to FIG. 4C, the method may include forming a bit-line contacthole 40 h and forming a bit-line contact plug 40 filling the bit-linecontact hole 40 h, by performing the processes described with referenceto FIGS. 3I and 3J.

Referring to FIG. 4D, the method may include, by performing theprocesses described with reference to FIGS. 3K to 3O, forming a bit-linebarrier layer 53 a, a bit-line electrode layer 54 a, and a bit-linecapping layer 55 a on the bit-line contact plug 40 by performing adeposition process, forming a bit-line structure 50 including a bit-linebarrier pattern 53, a bit-line electrode pattern 54, and a bit-linecapping pattern 55 by etching the bit-line capping layer 55 a, thebit-line electrode layer 54 a, and the bit-line barrier layer 53 a,forming a protection insulating layer 45 on a slanted surface of theexposed bit-line contact plug 40, forming a spacer layer 34 surroundingthe bit-line structure 50, forming an upper interlayer insulating layer35 on the spacer layer 34, forming capacitor contact holes 60 h, formingcapacitor contact plugs 60 filling the capacitor contact holes 60 h,forming an etch stop layer 36 on the capacitor contact plugs 60 and thespacer layer 34 or the bit-line capping pattern 55, forming a moldingoxide layer 37 on the etch stop layer 36, and forming capacitorelectrode holes 81 h vertically passing through the molding oxide layer37 and the etch stop layer 36 to expose the upper surfaces of thecapacitor contact plugs 60.

In an exemplary embodiment, the method may include, with reference toFIGS. 3O, 3P, and 2B, forming capacitor structures 80 includingcapacitor lower electrodes 81, a capacitor dielectric layer 83, andcapacitor upper electrodes 85, and a capacitor capping insulating layer38.

FIGS. 5A to 5C are vertical cross-sectional views taken along line I-I′of FIG. 1A or line II-II′ of FIG. 1B for describing a method offabricating a semiconductor device in accordance with an embodiment ofthe inventive concept.

Referring to FIG. 5A, a method of fabricating a semiconductor device100C in accordance with an embodiment of the inventive concept mayinclude, with reference to FIGS. 3A to 3E, forming device isolationregions 12 defining an active region 11 in a substrate 10, forming atrench mask layer 31 on the substrate 10, forming gate trenches 21 inthe substrate 10 by performing an etching process using the trench masklayer 31 as an etch mask, conformally forming a gate insulating layer 22on inner walls of the gate trenches 21 and a surface of the trench masklayer 31, conformally forming a gate barrier layer 23 a on the gateinsulating layer 22, forming a gate electrode layer 24 a filling thegate trench 21 on the gate barrier layer 23 a, forming a gate electrodepattern 24 and a gate barrier pattern 23 by partially removing upperportions of the gate barrier layer 23 a and the gate electrode layer 24a in the gate trench 21 by performing an etchback process, forming abuffer oxide layer 26 directly on the gate insulating layer 22 and thegate electrode pattern 24 in the gate trench 21, forming a gate cappinginsulating layer 27 filling the gate trench 21 on the buffer oxide layer26, and forming a source area 1 is and drain areas 11 d.

Referring to FIG. SB, the method may include forming a gate structure 20including the gate insulating layer 22, the gate barrier pattern 23, thegate electrode pattern 24, the electrode protection layer 25, and thebuffer oxide layer 26 in the gate trench 21 by removing the gate cappinginsulating layer 27 and the buffer oxide layer 26 which are disposed onthe trench mask layer 31 by performing a planarization process. Theplanarization process may include a CMP process. An upper surface of thetrench mask layer 31 may be exposed.

Referring to FIG. 5C, the method may include, by performing theprocesses described with reference to FIGS. 3H to 3Q, forming a lowerinterlayer insulating layer 32 and a hole mask layer 33, forming abit-line contact plug 40, forming a bit-line structure 50 including abit-line barrier pattern 53, a bit-line electrode pattern 54, and abit-line capping pattern 55, forming a spacer layer 34, forming an upperinterlayer insulating layer 35, forming capacitor contact plugs 60,forming an etch stop layer 36, and forming a capacitor structure 80including a capacitor lower electrode 81, a capacitor dielectric layer83, and a capacitor upper electrode 85.

The method may include forming a capacitor capping insulating layer 38with reference to FIG. 2C.

FIGS. 6A and 6B are vertical cross-sectional views taken along line I-I′of FIG. 1A or line II-II′ of FIG. 1B for describing a method offabricating a semiconductor device in accordance with an embodiment ofthe inventive concept.

Referring to FIG. 6A, a method of fabricating a semiconductor device100D in accordance with an embodiment of the inventive concept mayinclude, by performing the processes described with reference to FIGS.3A to 3E and FIG. 5A, forming device isolation regions 12 defining anactive region 11 in a substrate 10, forming a trench mask layer 31 onthe substrate 10, forming gate trenches 21 in the substrate 10 byperforming an etching process using the trench mask layer 31 as an etchmask, conformally forming a gate insulating layer 22 on inner walls ofthe gate trenches 21 and a surface of the trench mask layer 31,conformally forming a gate barrier layer 23 a on the gate insulatinglayer 22, forming a gate electrode layer 24 a filling the gate trench 21on the gate barrier layer 23 a, forming a gate electrode pattern 24 anda gate barrier pattern 23 by partially removing upper portions of thegate barrier layer 23 a and the gate electrode layer 24 a in the gatetrench 21 by performing an etchback process, forming a buffer oxidelayer 26 directly on the gate insulating layer 22 and the gate electrodepattern 24 in the gate trench 21, forming a gate capping insulatinglayer 27 filling the gate trench 21 on the buffer oxide layer 26,forming a source area 1 is and drain areas 11 d, forming a gatestructure 20 including the gate insulating layer 22, the gate barrierpattern 23, the gate electrode pattern 24, the buffer oxide layer 26,and the gate capping insulating layer 27 in the gate trench 21 byremoving the gate capping insulating layer 27, the buffer oxide layer26, the electrode protection layer 25, and the trench mask layer 31which are disposed on the substrate 10 by performing a planarizationprocess. A surface of the substrate 10 may be exposed. For example, thetrench mask layer 31 may be fully removed.

Referring to FIG. 6B, the method may include, by performing theprocesses described with reference to FIGS. 3H to 3M, forming a lowerinterlayer insulating layer 32 and a hole mask layer 33, forming abit-line contact plug 40, forming a bit-line structure 50 including abit line barrier pattern 53, a bit-line electrode pattern 54, and abit-line capping pattern 55, forming a spacer layer 34, and forming anupper interlayer insulating layer 35.

In an embodiment, the method may include, by performing the processesdescribed with reference to FIGS. 3N to 3Q and FIG. 2D, formingcapacitor contact plugs 60, forming capacitor structures 80 includingcapacitor lower electrodes 81, a capacitor dielectric layer 83, andcapacitor upper electrodes 85, and forming a capacitor cappinginsulating layer 38 covering the capacitor structures 80.

FIGS. 7A to 7D are vertical cross-sectional views taken along line I-I′of FIG. 1A or line II-II′ of FIG. 1B for describing a method offabricating a semiconductor device in accordance with an embodiment ofthe inventive concept.

Referring to FIG. 7A, a method of fabricating a semiconductor device100E in accordance with an embodiment of the inventive concept mayinclude, by performing the processes described with reference to FIGS.3A to 3E, forming device isolation regions 12 defining an active region11 in a substrate 10, forming gate trenches 21, conformally forming agate insulating layer 22 on an inner wall of the gate trench 21,conformally forming a gate barrier layer 23 a on the gate insulatinglayer 22, forming a gate electrode layer 24 a filling the gate trench21, forming a gate electrode pattern 24 and a gate barrier pattern 23 bypartially removing upper portions of the gate barrier layer 23 a and thegate electrode layer 24 a, and forming an electrode protection materiallayer 25 a filling the gate trench 21.

An upper end of the gate barrier pattern 23 may be recessed to be lowerthan an upper surface of the gate electrode pattern 24. The electrodeprotection material layer 25 a may fill a gap between the gateinsulating layer 22 and the gate electrode pattern 24 on the upper endof the recessed the gate barrier pattern 23. The electrode protectionmaterial layer 25 a may include silicon nitride.

Referring to FIG. 7B, the method may include forming an electrodeprotection layer 25 existing in a portion of the gate trench 21 andcovering the gate barrier pattern 23 and the gate electrode pattern 24,by removing an upper portion of the electrode protection material layer25 a by performing an etchback process.

Referring to FIG. 7C, the method may include forming a gate structure 20including the gate insulating layer 22, the gate barrier pattern 23, thegate electrode pattern 24, the electrode protection layer 25, the bufferoxide layer 26, and the gate capping insulating layer 27 by performingthe processes described with reference to FIGS. 3F and 3G.

The buffer oxide layer 26 may include N-type impurities such asphosphorus (P). Accordingly, the N-type impurities of the buffer oxidelayer 26 may diffuse into the active region 11 to form a source area 11s and drain areas 11 d in this process.

Referring to FIG. 7D, the method may include, by performing theprocesses described with reference to FIGS. 3H to 3M, forming a lowerinterlayer insulating layer 32, forming a bit-line contact plug 40,forming a bit-line structure 50 including a bit-line barrier pattern 53,a bit-line electrode pattern 54, and a bit-line capping pattern 55, andforming a protection insulating layer 45 on a slantly exposed surface ofthe bit-line contact plug 40. The protection insulating layer 45 mayinclude a native oxide. When the bit-line contact plug 40 is notpolysilicon, a process of forming the protection insulating layer 45 maybe omitted.

In an embodiment, the method may include, by performing the processesdescribed with reference to FIGS. 3M to 3Q and FIG. 2E, forming a spacerlayer 34, forming an upper interlayer insulating layer 35, forming atrench mask layer 31, forming capacitor contact plugs 60, forming anetch stop layer 36, forming a capacitor structure 80 including acapacitor lower electrode 81, a capacitor dielectric layer 83, and acapacitor upper electrode 85, and forming a capacitor capping insulatinglayer 38.

FIG. 8 is a vertical cross-sectional view taken along line I-I′ of FIG.1A or line II-II′ of FIG. 1B for describing a method of fabricating asemiconductor device in accordance with an embodiment of the inventiveconcept.

Referring to FIG. 8, a method of fabricating a semiconductor device 100Fin accordance with an embodiment of the inventive concept may include,by performing the processes described with reference to FIGS. 3A to 3Gand FIGS. 7A to 7C, forming device isolation regions 12 defining anactive region 11 in a substrate 10, forming gate trenches 21,conformally forming a gate insulating layer 22 on an inner wall of thegate trench 21, conformally forming a gate barrier layer 23 a on thegate insulating layer 22, forming a gate electrode layer 24 a fillingthe gate trench 21 forming a gate electrode pattern 24 and a gatebarrier pattern 23 by partially removing upper portions of the gatebarrier layer 23 a and the gate electrode layer 24 a, forming anelectrode protection material layer 25 a filling the gate trench 21,forming an electrode protection layer 25 existing in a portion of thegate trench 21 and covering the gate barrier pattern 23 and the gateelectrode pattern 24 by removing an upper portion of the electrodeprotection material layer 25 a, forming a gate structure 20 includingthe gate insulating layer 22, the gate barrier pattern 23, the gateelectrode pattern 24, the electrode protection layer 25, the bufferoxide layer 26, and the gate capping insulating layer 27, and forming alower interlayer insulating layer 32 directly on the substrate 10 andthe gate structure 20.

In an embodiment, the method may include, by performing the processesdescribed with reference to FIGS. 3H to 3Q and FIG. 2F, forming a holemask layer 33, forming a bit-line contact plug 40, forming a bit-linestructure 50, forming a spacer layer 34, forming an upper interlayerinsulating layer 35, forming a trench mask layer 31, forming capacitorcontact plugs 60, forming an etch stop layer 36, forming a capacitorstructure 80 including a capacitor lower electrode 81, a capacitordielectric layer 83, and a capacitor upper electrode 85, and forming acapacitor capping insulating layer 38.

FIG. 9 is a diagram conceptually showing a memory module 2100 includingat least one of the semiconductor devices 100A to 100F in accordancewith various embodiments of the inventive concept. Referring to FIG. 9,the memory module 2100 in accordance with the embodiment of theinventive concept may include a module substrate 2110, a plurality ofmemory devices 2120 disposed on the module substrate 2110, and aplurality of terminals 2130 arranged on a side of the module substrate2110. The module substrate 2110 may include a printed circuit board(PCB). The memory devices 2120 may include one of the semiconductordevices 100A to 100F in accordance with various embodiments of theinventive concept. The plurality of terminals 2130 may include a metalsuch as copper. Each of the terminals 2130 may be electrically connectedto each of the memory devices 2120. When the memory module 2100 includesmemory devices 2120 having a low leakage current and superior carriermobility, device performance may be improved.

FIG. 10 is a diagram conceptually showing a semiconductor module 2200 inaccordance with an embodiment of the inventive concept. Referring toFIG. 10, the semiconductor module 2200 in accordance with the embodimentof the inventive concept may include a processor 2220 mounted on amodule substrate 2210, and semiconductor devices 2230. The processor2220 or the semiconductor devices 2230 may include at least one of thesemiconductor devices 100A to 100F in accordance with variousembodiments of the inventive concept. Conductive input/output terminals2240 may be disposed on at least one side of the module substrate 2210.

FIG. 11 is a block diagram conceptually showing an electronic system2300 in accordance with an embodiment of the inventive concept.Referring to FIG. 11, the electronic system 2300 in accordance with theembodiment of the inventive concept may include a body 2310, a displayunit 2360, and an external apparatus 2370. The body 2310 may include amicroprocessor unit 2320, a power supply 2330, a function unit 2340,and/or a display controller unit 2350. The body 2310 may be a systemboard or mother board including a PCB and/or a case. The microprocessorunit 2320, the power supply 2330, the function unit 2340, and thedisplay controller unit 2350 may be mounted or arranged on a top surfaceor an inside of the body 2310. The display unit 2360 may be disposed thetop surface of the body 2310 or an inside/outside of the body 2310. Thedisplay unit 2360 may display an image processed by the displaycontroller unit 2350. For example, the display unit 2360 may include aliquid crystal display (LCD), an active matrix organic light emittingdiode (AMOLED), or various display panels. The display unit 2360 mayinclude a touch screen. Accordingly, the display unit 2360 may includean input/output function. The power supply 2330 may supply a current orvoltage to the microprocessor unit 2320, the function unit 2340, thedisplay controller unit 2350, etc. The power supply 2330 may include arechargeable battery, a socket for the battery, or a voltage/currentconverter. The microprocessor unit 2320 may receive a voltage from thepower supply 2330 to control the function unit 2340 and the display unit2360. For example, the microprocessor unit 2320 may include a CPU or anapplication processor (AP). The function unit 2340 may include atouch-pad, a touch-screen, a volatile/nonvolatile memory, a memory cardcontroller, a camera, a light, an audio and video playback processor, awireless transmission/reception antenna, a speaker, a microphone, a USBport, and other units having various functions. The microprocessor unit2320 or the function unit 2340 may include at least one of thesemiconductor devices 100A to 100F in accordance with variousembodiments of the inventive concept.

Referring to FIG. 12, an electronic system 2400 in accordance with anembodiment of the inventive concept may include a microprocessor 2414, amemory 2412, and a user interface 2418 which performs data communicationusing a bus 2420. The microprocessor 2414 may include a CPU or an AP.The electronic system 2400 may include a random access memory (RAM)2416, which directly communicates with the microprocessor 2414. Themicroprocessor 2414 and/or the RAM 2416 may be assembled in a singlepackage. The user interface 2418 may be used to input data to or outputdata from the electronic system 2400. For example, the user interface2418 may include a touch-pad, a touch-screen, a keyboard, a mouse, ascanner, a voice detector, a cathode ray tube (CRT) monitor, an LCD, anAMOLED, a plasma display panel (PDP), a printer, a light, or variousother input/output devices. The memory 2412 may store codes foroperating the microprocessor 2414, data processed by the microprocessor2414, or external input data. The memory 2412 may include a memorycontroller, a hard disk, or a solid state drive (SSD). Themicroprocessor 2414, the RAM 2416, and/or the memory 2412 may include atleast one of the semiconductor devices 100A to 100F in accordance withvarious embodiments of the inventive concept.

Semiconductor devices in accordance with various embodiments of theinventive concept may include a gate structure in which an upper end ofa gate barrier pattern is recessed to be lower than an upper end of agate electrode pattern. When the upper end of the gate barrier patternis recessed, a distance between the gate electrode pattern and a sourcearea and a distance between the gate electrode pattern and drain areasmay be increased. Accordingly, a GIRL current caused by turn-on of thegate structure may be decreased.

Semiconductor devices in accordance with various embodiments of theinventive concept may include a gate structure having a silicon oxidelayer. The silicon oxide layer may reduce a compressive stress that asilicon nitride layer of the gate structure applies on an active region(channel) of a substrate. Accordingly, reduction of carrier (electron)mobility can be reduced.

When the silicon oxide layer is softer and more flexible than thesilicon nitride layer, negative phenomena occurring due to a differencein thermal expansion coefficients between silicon and silicon nitridecan be prevented or reduced.

The silicon oxide layer may include N-type impurities such as phosphorus(P). The N-type impurities of the silicon oxide layer may diffuse andmove into the active region of the substrate through a diffusionprocess. Accordingly, a source area and drain areas with no physicaldamage may be formed in the active region.

The foregoing is illustrative of embodiments and is not to be construedas limiting thereof. Although a few embodiments have been described,those skilled in the art will readily appreciate that many modificationsare possible without materially departing from the present inventiveconcept. Accordingly, all such modifications are intended to be includedwithin the scope of this inventive concept as defined in the claims.

What is claimed is:
 1. A semiconductor device, comprising: a deviceisolation region defining an active region in a substrate; and gatestructures buried in the active region of the substrate, wherein atleast one of the gate structures comprises: a gate trench; a gateinsulating layer formed on an inner wall of the gate trench; a gatebarrier pattern formed on the gate insulating layer disposed on a lowerportion of the gate trench; a gate electrode pattern formed on the gatebarrier pattern and filling the lower portion of the gate trench; anelectrode protection layer formed on the gate insulating layer disposedon an upper portion of the gate trench and contacting the gate electrodepattern, wherein a bottom surface of the electrode protection layer isin contact with an upper surface of the gate barrier pattern and whereina portion of the electrode protection layer is disposed between the gateinsulating layer and the gate electrode pattern; a buffer oxide layerformed on the electrode protection layer; and a gate capping insulatinglayer formed on the buffer oxide layer to fill the upper portion of thegate trench, wherein the buffer oxide layer is U-shaped, and wherein abottom and side surfaces of the gate capping insulating layer arecovered by the buffer oxide layer.
 2. The semiconductor device of claim1, wherein the gate insulating layer is formed on the entire inner wallof the gate trench.
 3. The semiconductor device of claim 1, wherein theelectrode protection layer includes silicon nitride.
 4. Thesemiconductor device of claim 1, wherein the buffer oxide layer includessilicon oxide containing N-type impurities.
 5. The semiconductor deviceof claim 4, further comprising a source area disposed between the gatestructures, wherein the source area includes the same dopant as theN-type impurities included in the buffer oxide layer.
 6. Thesemiconductor device of claim 5, further comprising a bit-line contactplug vertically aligned with and overlapping the source area, wherein aside of a bottom surface and a bottom of a side surface of the bit-linecontact plug contacts the gate capping insulating layer, the bufferoxide layer, and the electrode protection layer.
 7. The semiconductordevice of claim 6, wherein a horizontal width of the bit-line contactplug is greater than a horizontal width of the source area.
 8. Thesemiconductor device of claim 6, further comprising a bit-line structuredisposed on the bit-line contact plug, wherein an upper surface of thebit-line contact plug exposed without being vertically overlapped by thebit-line structure is slanted.
 9. The semiconductor device of claim 8,further comprising a silicon oxide layer formed on the slanted uppersurface of the bit-line contact plug.
 10. The semiconductor device ofclaim 8, further comprising a lower interlayer insulating layer, whereinthe slanted upper surface of the bit line contact plug is recessed to belower than an upper surface of the lower interlayer insulating layer.11. The semiconductor device of claim 10, further comprising a spacerlayer covering the bit-line structure, wherein the spacer layer isformed on the slanted upper surface of the recessed bit-line contactplug.
 12. The semiconductor device of claim 1, wherein the gate cappinginsulating layer includes silicon nitride.
 13. The semiconductor deviceof claim 1, wherein an upper end of the gate barrier pattern is recessedto be lower than an upper end of the gate electrode pattern.
 14. Thesemiconductor device of claim 13, wherein a portion of the electrodeprotection layer is interposed between the gate insulating layer and thegate electrode pattern on the upper end of the recessed gate barrierpattern.
 15. A semiconductor device, comprising: gate structures buriedin a substrate; a bit-line contact plug formed on the substrate to bevertically aligned with the substrate between the gate structures; abit-line structure formed on the bit-line contact plug; and a spacerlayer covering the bit-line structure, wherein each of the gatestructures includes: a gate trench formed in the substrate; a gateinsulating layer formed on an inner wall of the gate trench; a gatebarrier pattern formed on the gate insulating layer disposed on a lowerportion of the gate trench; a gate electrode pattern formed on the gatebarrier pattern and filling the lower portion of the gate trench; asilicon oxide layer formed on the gate insulating layer disposed on anupper portion of the gate trench; a silicon nitride layer formed on thesilicon oxide layer to fill the upper portion of the gate trench,wherein the silicon oxide layer is U-shaped, and wherein a bottom andside surfaces of the silicon nitride layer are covered by the siliconoxide layer; and an electrode protection layer conformally formed arounda lower portion of the silicon oxide layer, wherein a bottom surface ofthe electrode protection layer is in contact with an upper surface ofthe gate barrier pattern, and wherein a portion of the electrodeprotection layer is disposed between the gate insulating layer and thegate electrode pattern.
 16. The semiconductor device of claim 15,further comprising a silicon nitride layer conformally formed betweenthe gate insulating layer and the silicon oxide layer.
 17. Thesemiconductor device of claim 15, wherein an upper end of the gatebarrier pattern is recessed to be lower than an upper end of the gateelectrode pattern, resulting in forming a gap between the gateinsulating layer and the gate electrode pattern, and a portion of thesilicon oxide layer fills the gap.
 18. The semiconductor device of claim15, wherein the silicon oxide layer includes phosphorus (P).
 19. Asemiconductor device, comprising: a device isolation region defining anactive region in a substrate; gate structures buried in the activeregion of the substrate; a bit-line contact plug formed on the substrateto be vertically aligned with the active region between the gatestructures; and a bit-line structure formed on the bit-line contactplug, wherein each of the gate structures comprises: a gate trenchformed in the substrate; a gate insulating layer formed on an inner wallof the gate trench; a gate barrier pattern formed on the gate insulatinglayer disposed on a lower portion of the gate trench; a gate electrodepattern formed on the gate barrier pattern and filling the lower portionof the gate trench; a silicon nitride layer formed on the gateinsulating layer disposed on an upper portion of the gate trench andcontacting the gate barrier pattern and the gate electrode pattern; asilicon oxide layer formed on the gate insulating layer disposed on theupper portion of the gate trench; and a gate capping insulating layerformed on the silicon oxide layer to fill the upper portion of the gatetrench, wherein an upper end of the gate barrier pattern is recessed tobe lower than an upper end of the gate electrode pattern, and a lowerportion of the bit-line contact plug protrudes downward to be lower thanan upper surface of the substrate to be in contact with the siliconnitride layer, the silicon oxide layer, and the gate capping insulatinglayer.
 20. The semiconductor device of claim 19, wherein the activeregion comprises: a source area disposed between the gate structures;and drain areas disposed between the device isolation region and thegate structures, wherein the silicon oxide layer, the source area, andthe drain areas include N-type dopants.